Taxonomy of Finfish

2.1.6.1 Paired fins

The pectoral, pelvic fins are the paired fins since they are two in numbers placed side by side. The pectoral fins- are inserted in most cases laterally but in some may be horizontally (Psilorhynchidae, some Homalopterids) or even above the ventral profile (perches, gobies) (Fig. 24 C). They bear the fin rays, simple and branched and in catfishes the pectoral spine. In some cases the fin rays may be elongated as long filaments (Fig. 24 D Ctenops nobilis). The shape of the pectoral fins vary differently.The pelvic fins (some times called ventral fins), are inserted in most cases ventrally and are placed with a distance in between them (Fig. 25 A), but in Gobiidae they are united. In Sicyopterus they are united in the form of a cup (Fig. 25 B) shaped disc. The fins bear the simple and branched rays.In Syngnathids they are much reduced. The fins are absent in some (eels, Mastacembelidae, Puffer fishes). In perches the fins when present may be thoracic (Fig. 24 A) or jugular (Fig. 24 B) in position and bear spines.

Fig. 24. Pelvic fin insertion. A. Thoracic. B. Jugular. C. Abdominal. D. with filaments Ctenops nobilis.

Fig. 25. Pelvic fins: A. Free. B. United as a cup (Gobioids).